32 USC § 107. Availability of appropriations
(a) Under such regulations as the Secretary concerned may prescribe, appropriations for the National Guard are available for—
(1) the necessary expenses of members of a regular or reserve component of the Army or the Air Force traveling on duty in connection with the National Guard;
(2) the necessary expenses of members of the Regular Army or the Regular Air Force on duty in the National Guard Bureau or with the Army Staff or the Air Staff, traveling to and from annual conventions of the Enlisted Association of the National Guard of the United States, the National Guard Association of the United States, or the Adjutants General Association;
(3) the transportation of supplies furnished to the National Guard as permanent equipment;
(4) the office rent and necessary office expenses of officers of a regular or reserve component of the Army or the Air Force on duty with the National Guard;
(5) the expenses of the National Guard Bureau, including clerical services;
(6) the promotion of rifle practice, including the acquisition, construction, maintenance, and equipment of shooting galleries and suitable target ranges;
(7) such incidental expenses of authorized encampments, maneuvers, and field instruction as the Secretary considers necessary; and
(8) other expenses of the National Guard authorized by law.
(b) The expenses of enlisted members of the Regular Army or the Regular Air Force on duty with the National Guard shall be paid from appropriations for the Army National Guard or the Air National Guard, as the case may be, but not from the allotment of a State, the Commonwealth of Puerto Rico, the District of Columbia, Guam, or the Virgin Islands. Payable expenses include allowances for subsistence and housing under sections 402 and 403 of title 37 and expenses for medicine and medical attendance.
(c) The pay and allowances for the Chief of the National Guard Bureau and officers of the Army National Guard of the United States or the Air National Guard of the United States called to active duty under section 12402 of title 10 shall be paid from appropriations for the pay of the Army National Guard or Air National Guard.